In applications with moving devices, for example rotating devices, it is often desired to obtain an information regarding a position of the moving device. The moving device may be configured as a rotating device and the position may be a rotating angle of the rotating device. The rotating device may comprise a magnet so that a rotating magnetic field is generated by the magnet during the rotation of the rotating device. In order to determine a current position of the rotating device during the rotary movement, a position sensor device which may be configured as a magnetic position sensor device may be used. The magnetic position sensor device may detect an evaluate the rotating magnetic field generated by the rotating magnet in order to provide an information regarding the position of the rotating device.
The magnetic position sensor device may be arranged in the proximity of the rotating magnet to detect the rotating magnetic field during the rotary movement of an axis of the rotating device. The magnet may, for example, be mounted to the axis of the rotating device. The position of the rotating device may be indicated by specifying the rotating angle of the rotating device. A predefined position of the rotating device may be defined as having a rotating angle of 0°. The rotating angles in the range between 0° and 360° indicate the position of the rotating device in relation to the 0° position.
The position sensor device may comprise a detection unit to detect a signal generated by the moving device and an evaluation unit to determine the position of the moving device. The position sensor device configured as magnetic position sensor device may comprise a detection unit to detect the magnetic field of the magnet and an evaluation unit to determine the position of the rotating device by evaluating the detected rotating magnetic field. The detection unit of the position sensor device may comprise optical sensors or magnetic sensors, such as Hall-sensors, and an analogue front-end comprising front-end amplifier, filter components etc. The evaluation unit may comprise an analogue-to-digital converter and a digital backend executing, for example, decimation filtering and a CORDIC algorithm. Both the analogue detection unit and the digital back-end of the evaluation unit introduce a delay during the calculation of the position of the moving device. This delay time is known as system propagation delay.
Due to this latency time between the measurement and evaluation of the signal generated by the moving device, for example a magnetic field vector, and the moment in time when the position of the moving device, for example the rotating angle of the rotating device, is available, for example through an SPI interface, the position sensor device can introduce a position error, for example an angle error. The position error is proportional to the speed of the moving device. In the example of a magnetic position sensor device, the angle error is proportional to the speed of the rotary movement of the rotating device. In high speed applications the contribution of the dynamic position error can be substantially big. Since reducing the latency of the position sensor would increase the output noise, it is in general not possible to reduce the system propagation delay.
In a medium resolution magnetic position sensor device having, for example a resolution of 10 bit, the error occurred during the calculation of the rotating angle represents already a few LSBs at highspeed rotation. In addition there are several applications where the maximum speed is also substantially higher. This error contribution generally does not allow employing such a sensor. Furthermore, magnetic position sensors with a high resolution slow core, for example sigma delta based, need an embedded interpolator which introduces a further source of delay.
It is desirable to provide a position sensor device to determine a position of a moving device which enables to compensate the position error obtained during the determination of the position due to a propagation delay time of the position sensor device. Furthermore, there is a desire to specify a method to determine a position of a moving device which enables to compensate the position error obtained during the determination of the position due to a propagation delay time of the position sensor device.